Earlier diagnosis, improved treatment, and the overall increase in longevity in later life continue to expand the number of breast cancer survivors who are 65+ years of age, already estimated to be one million (43%) of the total 2.3 million breast cancer survivors. This group of older breast cancer survivors represents 17% of all older cancer survivors, yet the impact of breast cancer and its treatment on survivorship is poorly understood. The parent study (Breast Cancer Treatment Effectiveness in Older Women - BOW I) studied 1859 women 65+ years of age with early stage breast cancer and provided strong evidence that variations in care have substantial consequences for older women: less-than-standard treatment is associated with increased rates of recurrence and breast cancer-specific mortality,while mammography surveillance during the first 5 years after diagnosis is associated with a reduced rate of breast cancer mortality. However, little is known about the effectiveness of mammography surveillance for recurrence and second primaries beyond five years;the cost implications associated with short-term and long-term survivorship care;and the risk of late treatment effects. Responding to the survivorship research priorities of the National Cancer Institute (NCI) and the Institute of Medicine (IOM) to understand and reduce the adverse effects of cancer treatment in older adults, this renewal project (BOW II) will collect additional information about the BOW I breast cancer cohort through 15 years after diagnosis. A comparison cohort of women without breast cancer will be enrolled and matched on age, study site, and breast cancer diagnosis year that will be followed for the same period of time. We will characterize the survivorship of older breast cancer patients and in relation to a comparison cohort cared for in integrated health care systems through the efficient collection of data from medical records and electronic sources. This uniquely detailed dataset, collected by an experienced interdisciplinary team of investigators, will provide new knowledge in three domains of survivorship research: follow-up care, health care costs, late effects of treatment. Both BOW I and II take advantage of the resources of the recently renewed Cancer Research Network (CRN). BOW specific aims will be: (1) To determine whether surveillance mammography beyond 5 years following diagnosis reduces breast cancer-specific mortality, and explore whether surveillance mammography is cost-effective. (2) To determine the cost-effectiveness of standard primary tumor therapy (breast conserving surgery [BCS] followed by radiation therapy or mastectomy) and adjuvant (tamoxifen) therapy, compared with less-than- standard therapy, for older women with breast cancer. (3) To identify late effects of breast cancer and its treatment by comparing incident comorbidity in 5-year breast cancer survivors to a matched comparison cohort without breast cancer. PUBLIC HEALTH RELEVANCE: The average age of all cancer patients is 70 years, and this is projected to increase to 75 years by 2030. BOW II will characterize the survivorship of older breast cancer patients cared for in integrated health care systems where complete data collection through 15 years of follow-up can be accomplished efficiently. It will provide much needed evidence about the effectiveness of surveillance mammography and the occurrence of late effects which, together with cost analyses, will inform the design of systems changes to promote evidence- based survivorship care for older breast cancer survivors.